Vagalume is a Last.fm client for the Gnome desktop environment and the Maemo platform, used by the Nokia 770/N800/N810 Internet Tablets

gPodder downloads and manages free audio and video content ("podcasts") for you. Listen directly on your computer or on your mobile devices.

Available for Linux, FreeBSD, Windows, Mac OS X and mobile devices like the Nokia N810, N900 and N9.

Tsung is an open-source multi-protocol distributed load testing tool. It is protocol-independent and can currently be used to stress test HTTP, SOAP PostgreSQL, and Jabber servers.

Fldigi (Fast Light Digital modem application) is a program for transmitting and receiving signals via a radio transceiver. It includes support for most digital modes used on the amateur radio bands, as well as many related functions (logging, transceiver control, sound card calibration and frequency analysis)....

gtk-gnutella is the most advanced server/client for Gnutella, in terms of protocol features supported and algorithms used.
It runs on every Unix-like system which supports GTK+ (1.2 or above). The GNOME desktop environment is not required. It is currently developed and tested under Linux (Debian) as well as NetBSD. It is known to run at least on Linux, FreeBSD, NetBSD, OpenBSD, Darwin, Solaris, Tru64 UNIX (OSF/1), SGI IRIX, BeOS whereas CPU architectures include x86, AMD64, PowerPC, SPARC, MIPS....

MapGuide Open Source is a web-based platform that enables users to quickly develop and deploy web mapping applications and geospatial web services. MapGuide features an interactive viewer that includes support for feature selection, property inspection, map tips, and operations such as buffer, select within, and measure. MapGuide includes an XML database for managing content, and supports most popular geospatial file formats, databases, and standards. MapGuide can be deployed on Linux or Windows, supports Apache and IIS web servers, and offers extensive PHP, .NET, Java, and JavaScript APIs for application development....

a GUI builder for wxPython/wxWidgets written in Python,

Plagger is a pluggable RSS/Atom feed aggregator and mashup creating software, written in pure Perl.

Caliburn.Micro is a small, yet powerful framework, designed for building applications across all XAML platforms. With strong support for MVVM and other proven UI patterns, Caliburn.Micro will enable you to build your solution quickly, without the need to sacrifice code quality or testability....

MediaPortal turns your HTPC into a very advanced media center, or Home Theater PC (HTPC):

- Listen to music and radio
- Play videos, movies and DVDs
- View pictures or create a slideshow
- Watch, schedule and record live TV - like a TiVo, but more, and for free! ...